fix: Rewrite "No metadata found" error more clearly, adding explanation that perhaps a using codebase is implemented but no flags have been written

[capndave]

Description

src/validation/ValidationExecutor.ts conditionally returns the following error: No metadata found. There is more than once class-validator version installed probably. You need to flatten your dependencies. There are two issues with this error.

• the error has typos/incorrect grammar. "There is more than once class-validator version installed probably" should instead read "There are probably more than one class-validator versions installed", or "There are probably multiple class-validator versions installed"
• This error sometimes arises when a developer uses a module as a dependency that itself depends on class-validator, but the developer has not yet used a class-validator flag in their file or codebase. One such case is documented in a type-graphql issue, for example.

Proposed Solution

Update the error message with correct grammar and add a sentence explaining that validation flags are expected but not present in the code.

[NoNameProvided]

The error message is now updated to the following:

No validation metadata found. No validation will be  performed. There are multiple possible reasons:` 
  - There may be multiple class-validator versions installed. You will need to flatten your dependencies to fix the issue.
  - This validation runs before any file with validation decorator was parsed by NodeJS.

[NoNameProvided]

This feature/fix has been released in 0.14.0.

[github-actions]

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